[R] Volume of polygon

[Bert Gunter]

The volume of a polygon  = 0.  Polyhedra  have volumes.

This may be irrelevant, but if the lake is cylindrical == constant cross
sectional area at all depths, then height doubles when the volume does and
vice versa.  Otherwise you have to know how area varies with height or use
more sensible approximations thereto.

Cheers,
Bert

On Tue, Dec 5, 2023, 20:13 javad bayat <j.bayat194 using gmail.com> wrote:

>  Dear all;
> I am trying to calculate the volume of a polygon shapefile according to a
> DEM raster. I have provided some codes at the end of this email.I dont know
> if the codes are correct or not. Following this, I have another question
> too.
> I want to know if the volume of the reservoir rises or doubles, what would
> be the elevation?
> I would be more than happy if anyone could help me.
> Sincerely
>
> "
> library(raster)
> library(terra)
> library(exactextractr)
> library(dplyr)
> library(sf)
> r <- raster("Base.tif")
> p <- shapefile("p.shp")
> r <- crop(r, p)
> r <- mask(r, p)
> x <- exact_extract(r, p, coverage_area = TRUE)
>
> x1 = as.data.frame(x[1])
> head(x1)
> x1 = na.omit(x1)
>
> x1$Height = max(x1[,1]) - x1[,1]
>
> x1$Vol = x1[,2] * x1[,3]
>
> sum(x1$Vol)
>
> "
>
> --
> Best Regards
> Javad Bayat
> M.Sc. Environment Engineering
> Alternative Mail: bayat194 using yahoo.com
>
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>
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